The long range goal is to characterize the molecular and cellular mechanisms that are responsible for local biosynthesis of estrogen in endometriosis. The findings of our preliminary studies include (i) significant levels of aromatase P450 (P450arom) mRNA, protein and activity in stromal cells of endometriotic tissue but not in eutopic endometrium; (ii) P450arom gene expression directed by promoter II and aromatase activity in endometriotic stromal cells are induced strikingly by PGE2 via EP2 receptors or by cAMP analogs; (iii) differential binding of stimulatory (SF-1) and inhibitory (COUP-TFs) transcription factors upstream of promoter II account for the difference in aromatase expression in endometriotic and eutopic endometrial stromal cells; (iv) an unusually severe case of recurrent postmenopausal endometriosis resolved after treatment with an aromatase inhibitor. Thus, molecular aberrations in endometriotic tissue in contrast to eutopic endometrium give rise to increased local concentration of estrogen that promotes the growth and development of pelvic endometriosis. To determine the molecular basis for estrogen and PGE2 formation and estrogen action in endometriosis, we propose the following studies: Initially, we will characterize regulatory elements and differential binding of nuclear proteins to these sequences upstream of P450arom promoter II in endometriotic and eutopic endometrial stromal cells using deletion mutations of this regulatory region, site-directed mutagenesis and electrophoretic mobility shift assays. Transcription factors that bind to these regulatory sequences will be defined and their roles will be characterized in the regulation of aromatase expression in endometriotic stromal cells. This will be accomplished by screening expression libraries using DNA binding sites as probes and determining the effects of these factors on promoter II activity and aromatase expression. We will define mechanisms whereby PGE2 action and production are regulated in endometriotic tissue. The regulation of expression of EP2 receptors and COX-2 will be evaluated in both endometriotic tissue and eutopic endometrium. Finally, the in vivo significance of local estrogen biosynthesis and estrogen (and progesterone) action will be determined in a mouse model of endometriosis. The rate of formation and the site of surgically transplanted endometriotic lesions will be quantified in transgenic mice with disrupted genes of P450arom, estrogen receptor-alpha and progesterone receptor. The role of aromatase inhibitors in the treatment of endometriosis (in comparison with conventional treatments) will also be characterized in this model.